Tuesday July 9, 2013
Noon – 1  pm
Texas Instruments (TI) Auditorium E-1
2900 Semiconductor Drive
Santa Clara, CA
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TITLE: Splitting One Photon to Two Electrons: Toward Breaking the Single Junction Efficiency Limit

SPEAKER: Dr. Jiye Lee, Postdoctoral fellow in the Molecular Foundry at LBNL

ABSTRACT:
Conventional solar cells generate one electron for each absorbed photon. Any excess photon energy above the bandgap is wasted as heat. This fundamental energy loss imposes the Shockley-Queisser limit of 34% for single optimized semiconductor junction. Singlet fission, a nanoscale process in organic molecules, splits a high-energy molecular excitation into a pair of low-energy ones. In solar cells, it promises to double the electricity generated from the blue part of the sunlight, breaking the single junction efficiency limit.

I will present fission-based photovoltaic cells that produce more than one electron per photon. This is the first time that any solar cell has shown the peak photon-to-electron conversion efficiency exceeding 100% in the visible spectrum. To further advance fission-enhanced solar cell nanotechnology, it is crucial to understand the fundamental mechanism governing singlet fission. I will report on a universal mechanism that predicts the rate of singlet fission and confirm that fission is robust to variations in molecular nano-morphology.

SPEAKER BIOGRAPHY:
Jiye Lee is currently a postdoctoral fellow in the Molecular Foundry at Lawrence Berkeley National Laboratory. She received her PhD in electrical engineering from MIT. Her PhD thesis won the Microsystems Technology Laboratories Doctoral Dissertation Seminar at MIT. She obtained her B.S. in electrical engineering from KAIST in South Korea in 2006. She spent a summer in 2011 at Palo Alto Research Center.Her research interests are optoelectronics and photovoltaics based on nanomaterials, including organic molecules.

AGENDA:

• 11:30 am – Registration & light lunch (pizza & drinks)
• Noon – Presentation & Questions/Answers
• 1:00 pm – Adjourn